Running the LDU board in a P85 piggyback

[Troubled81]

I am modifing my P85+ (it identifies asa P90+ now as it has had the battery replaced with 7/8th 90kWh 350V p100D battery) for 1/8mile no prep and I want to run this board in a piggyback style were I will make a harness that taps all the input signals to the OG board in the car to keep it happy but have this board actually control the inverter.

SO the big question is can i keep the stock board in the car getting all of its input signals and not have it hooked up to drivers in the inverter without damaging it? would I need to add resistors or capacitors to the outputs? What could go wrong here?

I am doing this because I have tried a tuner box that did infact raise the output from 330kW to as high as 408kW but there is something holding the car back as the time to get from x to y rpm did not chage at all (7000-8000rpm top of peak power with this battery) even though is was pulling 70kW+ more power. The only thing that makes sence to me is that the OEM board is not letting the motor to move through the RPM any quicker even though it has more power as it needs the frequancy to change to raise the rpm. This was sort of confirmed as the 1/8mile times are the exact same from 75-100% soc with the tuner now were it would fall off before when you got into the low 90's.

I have confirmed that the BMS will let me pull 1400amps without issue with the tuner (stock was 1200amps). I am going to pull the pryo fuse to see if this battery has the same pryo fuse as a P100d that will let me pull up to 1800+ amps as this car now has the same modules in it as a P100D (just 14 instead of 16)

I am a mechanical engineer so this angry pixies stuff is way out of my wheel house. I have designed a bunch of mechanical parts for the LDU to help cooling and am looking to get them made, as well as have a list of more. The truth though is that I could use some help on the electronic side. I want this car hanging the front tires and to do this I will need more then the slicks and skinnies fitted to the car.

[P.S.Mangelsdorf]

Generally speaking, this board is not intended to work with the stock control board.

I'm not an EE either, (I'm in acoustics so related to ME), so I think I can help detail some of this. Others with more technical knowledge feel free to correct me.

First, we have to understand the two main ways to control the Tesla LDU in a manner other than stock.

• Emulation

• Replacement

Emulation is when the control board acts like the rest of the car, "tricking" the LDU into operating with out the rest of the car. This is the solution used by EVControl and by HSR Motors/057 Tech.

Replacement removes the Tesla brain from the LDU, and adds in our own brain that gives us full control over all of the parameters. This is the solution used by AEM and Open Inverter.

For what you want to do, it sounds like this car is a dedicated race car. If that is correct, than it may be worth considering using a replacement board. This would likely mean that you would need to find new or modified control systems for other HV parts of the car, or get good CAN logs from the LDU before the swap, so you can feed the rest of the car what it wants.

You might be able to use an emulation board to push the motor further, but again the rest of the car may get quite unhappy.

If you don't want to run the risk of the rest of the car having issues, you probably need to find someone that can reprogram and/or modify the stock control systems. To the best of my knowledge, there are 1-3 shops in the US that can do this. The one with the most documented success modifying the Model S firmware is Jason Hughes at HSR Motors/057 Tech. Unplugged Performance may also be able to help.

To be frank, you're in a bit of uncharted territory. I think that more will join you soon, but I think you may need to find some EE or CE friends who can help break some new ground in that space.

[muehlpower]

As I understand it, the OI board should be built into the LDU and control the motor. The original LDU board mounted outside the drive unit and connected to the car to make the rest of the car happy.

[Troubled81]

As I understand it, the OI board should be built into the LDU and control the motor. The original LDU board mounted outside the drive unit and connected to the car to make the rest of the car happy.

This is correct, the thing I am not sure about is the issues that will arise from having the OEM board powered and talking but no inverter control hooked up to anything. Is there going to be an issue splitting the sensor signals to two different boards?

The long term plan is to pull the Tesla VCU out, add a higher voltage lighter weight battery, and more powerful inverter in. But for now I want to see what I can get from this odd duck 350v P90+. This weekend I am going to pull the pyro fuse to understand how much Tesla will let out of the battery.

[muehlpower]

I think the live parameters are the problem. Temperature is easy. I don't know what happens when the LDU reports a stopped engine with 0 amps and the car is still moving quickly. Maybe you can test that by simply removing the drive shafts and towing the car

[Troubled81]

Can I not tap the encoder throttle, brake and shunt outputs into the OEM board so that it has the complete package? Or would there be issues with tapping into these signals?

[johu]

You could come up with some Y-connector to achieve that but the OEM control board will find it has no control over the currents as it's disconnected from the PWM. Quite sure it will error out but you never know until you try it.

[Troubled81]

So outside of the software error it should not damage anything?

Let me ask this a different way.

On the open inverter board would it get damaged if we tried to run it without being hooked up to the IGBT'S boards?

If I reversed this plan and y-connected the OI board to get all the inputs but not the output to the IGBT'S would I let the smoke out? And if it would let the smoke out what would I need to do to stop that from happening?

[Troubled81]

Ok, I have been reading prints and learning and I feel that I might have got past the "OMG this guy should not be touching this stuff" to a level of "wow you are dumb". (I have watched the videos and know that the board is fine to run without being hooked to the gate boards)

I hope to discuss the issue I have now, I have mapped out the pins going in and figured out what the OEM Needs and what the Open Inverter needs.

I need to make a PCB board that will split the input signals to the 2 boards and also takes the CANbus data and outputs the following:
-a +12v Forward signal to Open Inverter baord pin 7
-a +12v reverse signal to Open Inverter baord pin 8
-a +12v cruise signal to Open Inverter baord pin 21

Can the Open Inverter board take the Canbus data and go from forward/Reverse/Cruise removing this ablity from the pcb splitter board?
Has anyone used the tesla OEM shifter and cruise control stakl to control the Open Inverter board? ( I searched but did not find a thread on this)

Edit: I found this from wk057
CAN3, ID 0x0116
● Description: Rear drive unit torque and statusinfo
● Length observed: 6 bytes
● Frequency on bus: Approximately 100 Hz
● Example frames: 5A 44 75 44 8E FC
○ gear: 4 (D)
○ gearRequest: 4 (D)
○ torqueEstimate: 557 Nm (410.82 ft/lb)
○ vehicleSpeed: 32.05 MPH
● Value descriptions:
○ torqueEstimate = ((byte0 + ((byte1 & 0xF)<<8)) ­ (512 * (byte1 & 0x8))) / 2
○ Value is in Nm, signed 12­bit
■ Convert to ftlb with * 0.737562149
○ vehicleSpeed = ((byte2 + ((byte3 & 0xF)<<8)) ­ 500) / 20
■ MPH, 0.05 MPH resolution
○ gearRequest = (byte3 & 0x70)>>4
○ gear = (byte1 & 0x70)>>4
■ For both of the above: 0,5,6,7 = Invalid; 1=Park;2=Reverse;3=Neutral;4=Drive

Can the Open Inverter board use this data directly?

[P.S.Mangelsdorf]

Can the Open Inverter board take the Canbus data and go from forward/Reverse/Cruise removing this ablity from the pcb splitter board?
Has anyone used the tesla OEM shifter and cruise control stakl to control the Open Inverter board? ( I searched but did not find a thread on this)

Edit: I found this from wk057
CAN3, ID 0x0116

Can the Open Inverter board use this data directly?

Yes, the OI board can take direction via CAN assuming you know the CAN messages the car is sending. Though recent firmware has changed how that is done.
https://openinverter.org/wiki/CAN_communication